Unmanaged devices Ubuntu 18.04 with installed openbox

Question

I have installed on ubuntu 18.04 server edition manually the xorg, nm-applet and openbox wm and over the ~/.config/openbox/autostart I have the following settings:

dbus-launch nm-applet&
lxpanel &

But when I try to click on network-manager icon I get the error:

Ethernet Network Device Not Managed

So I tried any trick shown in the following questions:

• Ethernet device not managed
• network manager says "device not managed"

After having installed ifupdown:

sudo apt install ifupdown

and purging netplan:

sudo apt purge nplan

But I fail to make the nm-applet to manage my ethernet device. Can you help me?

Edit 1:

I reinstalled the nplan and I put the following configuration into /etc/netplan/50-cloud-init.yaml:

network:
  version: 2
  renderer: NetworkManager

But I still have probs to tame it.

Answer 1

The root of your problem is the netplan network management. In order to fix that switch into ifupdown by typing the following commands:

sudo systemctl stop networkd-dispatcher
sudo systemctl disable networkd-dispatcher
sudo systemctl mask networkd-dispatcher
sudo apt-get purge nplan netplan.io
sudo apt-get install ifupdown

And make them managed by following the answers seen in the following questions:

• Ethernet device not managed
• network manager says "device not managed"